Module 34 - Skeletal Muscle Gross Anatomy Pt.2

Function of arm muscles

Attach the arm to the thorax (thoracic cage)

3 Main arm muscles

1. Pectoralis major

2. Latissimus dorsi

3. Deltoid

Pectoralis Major - Structure + Movements

• Structure: anterior muscle

  • Fan-shaped, broad origin on thoracic cage

  • Insertion on the lateral side of the humerus, wrapping from the front

• Movements (of the arm): flexion, adduction, medial rotation

  • Assists with extension if the arm is already flexed

Lats - Structure + Movements

• Structure: large posterior muscle

  • Broad origin down the vertebral column

  • Passes under the axillary region to insert on anteiror humerus

• Movements: extension (prime mover), adduction, medial rotation

Deltoid - Structure + Movements

• Structure: triangular muscle that forms a cap over the shoulder joint

  • Broad origins on scapula + clavicle and inserts on lateral humerus

• Movements: abduction, flexion/extension, medial/lateral rotation

Name the rotator cuff muscles

SITS

• Supraspinatus

• Infraspinatus

• Teres minor

• Subscapularis

Main functions + Movements of the rotator cuff

• Hold the head of the humerus in the glenoid cavity

• Form a cap over proximal humerus

• Enable abduction, adduction, and rotation

Infraspinatus – Location, Insertion, Movement

• (Muscle belly) Located in infraspinous fossa
• Inserts on lateral humerus
• Movement: lateral rotation

Subscapularis – Location, Insertion, Movement

• Located in subscapular fossa (anterior side
• Inserts on anterior humerus
• Movement: medial rotation

Supraspinatus – Location, Insertion, Movement

• (Muscle belly) Located in supraspinous fossa
• Inserts on superior humerus (greater tubercle)
• Movement: abduction

Teres Minor – Location, Insertion, Movements

• Small, rounded muscle bellt below infraspinatus
• Inserts on greater tubercle
• Movements:
 – Adduction
 – Lateral rotation
 – Assists with extension

Forearm Extensors Muscles - Structure + Movement

• Triceps brachii – posterior humerus

  • 3 heads

  • inserts on olecranon process of ulna

  • extends forearm

• Anconeus – small posterior muscle extending from distal humerus to olecranon/ulna

  • Assists extension

Name the 3 Forearm Flexors

1. Biceps Brachii

2. Brachioradialis

3. Brachilais

Biceps - Structure + Functions

• Structure:

  • 2-headed muscle on anterior humerus

  • Origins on scapula + Inserts on radius

• Movements: flexion + supination

Brachioradialis - Structure + Movement

• Structure: most of muscle belly in the forearm

  • Originates in distal humerus + inserts on radius

• Movement: Flexion

Brachialis - Structure + Movement

• Structure: Deep to biceps

  • Originates on mid humerus + Inserts on ulna

• Movement: Flexion

Muscles involved in Supination - Structure + Movement

• Biceps

• Supinator: posterior, deep muscle, extends from ulna/humerus to radius

  • Movement: supination

2 muscles involved in Pronation - Structure

• Pronator quadratus: anterior distal side, between ulna and radius

• Pronatetor teres: anterior side, running opposite to supinator

Extrinsic Muscles of the Hand + Features

• Muscles with at least 1 origin outside the hand
• Muscle bellies are in the forearm (not hand)
• Long tendons extend into the hand and fingers
• Purpose: preserve manual dexterity

Movements of the anterior forearm muscles

• Flexion of wrist, hand + fingers

• Abduction + Adduction of wrist

• Tendones travel to the distal phalanges

Movements of Posterior Forearm Muscles

• Uses long tendons to move

• Extension of wrist, hand and fingers

• Abduction

Intrinsic Muscles of the hand + Features/Movements

• Muscles that originate + insert in the hand

• Smaller muscle bellies

• Overall movements: adduction, abduction, opposition, reposition

2 intrinsic muscle of the hand + Their movements

• Thenar Muscles

  • Located on the thumb side (fleshy part of thumb)

  • Movement: Opposition

• Hypothenar Muscles

  • Located on pinky side

  • Movement: Assist in opposition, adduction, abduction

Where do the thigh muscles originate and insert?

• Originate: Coxa (hip)

• Insert: Femur

Hip flexors are found on which side (anterior/posterior)?

Anterior

What muscles make up the hip flexors? + Movement

• Iliacus + Psoas Major = Iliopsoas
• Located on anterior side of hip
• Share common tendon of insertion on proximal femur
• Movement: flexion of thigh

What composes the posterolateral muscles of the thigh? + Movements

• Gluteals

• Tensor Fasciae Latae

• Movements: Extension and abduction of thigh, flexion + stabilize femur

Gluteal muscles (3) + Movements

• All on the posterior/lateral side

1. Gluteus Maximus: most superficial + largest

• Movements: extension, abduction, lateral rotation

2. Gluteus Medius: deep to maximus

• Movements: abduction

3. Glueteus Minimus: deepest gluteal muscle

• Movements: Abduction

Tensor Fasciae Latae - Structure & Movements

• Structure: small muscle belly with long tendon, crosses the knee

  • Originates on lateral thigh > crosses hip + knee joint > inserts onto leg bones

• Movement: flexion, abduction, stabilizes femu when standing

Deep Thigh Rotators – Function

• Responsible for lateral rotation of thigh

Sartorius - Structure + Function

• Part of muscles that move the leg + thigh muscles

• Structure: Runs lateral → medial across thigh

• Function: cross-legged position

  • When contracting:
     – Hip flexion
     – Lateral rotation of thigh
     – Knee flexion

Medial Thigh Muscles - Structure + Movement

• Part of muscles that move the leg + thigh muscles

• Structure: Run from hip → medial femur

• Movement: adduction of thigh

Name the muscles that move the leg

1. Hamstrings: posterior of thigh

   1. Biceps femoris: lateral and superificial

   2. Semitendinosus: Medial superficial

   3. Semimembranosus: deep

What movements do the hamstrings produce?

• Flexion of knee

• Extension of hip

• Biceps femoris performs lateral rotation of leg

Leg extensors at the knee: Quadriceps femoris - Muscles + Structure + Movement

• Anterior surface of thigh

  • Rectuc femoris: also does hip flexion

    • Originates at the hip

  • Vastus intermedius

    • Originates on femur

  • Vastus medialis

    • Originates on femur

  • Vastus lateralis

    • Originates on femur

• Movement: Extension of the leg at the knee

All 4 quads muscles (leg extensors) joint into the…

Patellar tendon, covering the patella

• Inserts on and around patella

• Then continues as the patellar ligament

Where does the patellar ligament insert?

Tibial tuberosity

• So it extends from the patella to the tibial tuberosity

Name the 3 compartments of the leg

• Anterior compartment

• Lateral compartment

• Posterior compartment: contains

  • superficial muscles

  • Deep muscles

Anterior compartment - Muscles + Movements

• Muscle: extensors

• Movements: dosriflexion, eversion, inversion of foot + extension of toes

Lateral compartment - Movement

• Plantar flexion

• Eversion

Posterior compartment - Muscles + Movement

• Largest compartment, with superificial + deep groups

• 3 Superificial Muscles: their fascia merge into calcaneal tendon (achilles tendon)

  • Gastrocnemius: 2 heads, most superficial

  • Soleus: deep to gastrocnemius

  • Plantaris: small, high muscle (extends from heel-ish to back of knee ish)

    • Movement: plantar flexion

• Deep muscles:

  • Movement: plantar flexion, inversion, flexion of toes

Extrinsic muscles of the foot - Structure + Movement + Function

• Structure: Long muscle bellies in the leg with long tendons (reaching the toes)

  • Originates + inserts within the foot

• Movement: flexion, extension, abduction, adduction of toes

• Function: support the body’s weight, creat arches of foot, help with locomotion